Matriptase degrades extracellular matrix. According to SWISS-PROT, it is proposed to play a role in breast cancer invasion and metastasis. It exhibits trypsin-like activity as defined by cleavage of synthetic substrates with Arg or Lys as the P1 site. It has an essential physiological role in profilaggrin processing, corneocyte maturation and lipid matrix formation associated with terminal differentiation of the oral epithelium and the epidermis and is also critical for hair follicle growth. It is a type II transmembrane serine protease expressed in most human epithelia and it is a strictly epithelial protease. It is expressed in carcinomas of epithelial origin and not in tumours of mesenchymal origin. Matriptase has previously been described in WO2009/020645.